DeMint, a fiscal conservative who has been at odds with House Speaker John Boehner over his willingness to compromise with the president on tax hikes, will leave to replace Ed Feulner as president of the Heritage Foundation.

The growing isolation of Grover Norquist, founder of Americans for Tax Reform and author of the “Taxpayer Protection Pledge,” has been talked about so often it’s hard to remember how little evidence there is for it.